One type of extracorporeal blood processing is an apheresis procedure in which blood is removed from a donor or patient, directed to a blood component separation device (e.g., centrifuge), and separated into various blood component types (e.g., red blood cells, white blood cells, platelets, plasma) for collection or therapeutic purposes. One or more of these blood component types are collected (e.g., for transfusion purposes), while the remainder are returned to the donor or patient. An example of an apheresis system is that disclosed in U.S. Pat. No. 6,319,471, incorporated herein by reference to the extent not inconsistent herewith.
A number of factors affect the commercial viability of an apheresis system. One factor relates to the operator of the system, specifically the time and/or expertise required of an individual to prepare and operate the apheresis system. For instance, reducing the time required by the operator to load and unload the disposables, as well as the complexity of these actions, can increase productivity and/or reduce the potential for operator error. Moreover, reducing the dependency of the system on the operator may lead to reductions in operator errors and/or to reductions in the credentials desired/required for the operators of these systems.
Donor-related factors may also impact the commercial viability of an apheresis system and include donor convenience and donor comfort. For instance, donors typically have only a certain amount of time which may be committed to visiting a blood component collection facility for a donation. Consequently, once at the collection facility the amount of the donor's time which is actually spent collecting blood components is another factor which should be considered. This also relates to donor comfort in that many view the actual collection procedure as being somewhat discomforting in that at least one and sometimes two access needles are in the donor throughout the procedure.
Performance-related factors continue to affect the commercial viability of an apheresis system as well. Performance may be judged in terms of the “collection efficiency” of the apheresis system, which may in turn reduce the amount of donation time and thus increase donor convenience. The “collection efficiency” of a system may of course be gauged in a variety of ways, such as by the amount of a particular blood component type which is collected in relation to the number of this blood component type which passes through the apheresis system. Performance may also be evaluated based upon the effect which the apheresis procedure has on the various blood component types. For instance, it is desirable to minimize the adverse effects on the blood component types as a result of the apheresis procedure (e.g., limit hemolysis and platelet activation).
A particularly important performance-related factor involves the control of the access or draw pressure of the blood being drawn from the donor or patient. Properly maintained access/draw pressures contribute to the reduction of donation times and the minimization of donor/patient discomfort. Also, certain access/draw pressure conditions signify no flow or improper flow characteristics which should be addressed by an operator. For example, it is well known that the access/draw needle may become improperly seated or blocked within the donor/patient access site. Access/draw pressures sensed by the apheresis system can be interpreted as indicating such a problem and then activating an alarm for operator intervention and/or pump controls such as pump slowing or stoppage.